My gig was showing in search results in online sellers but it got disappeared after a week I am getting orders and i have a 5-star rating? What can be the reason? Should I change the tags and my gig title or should I promote it for ranking?
Seniors, please tell
If you use the search 
you will find a lot of information on this topic.
Can you suggest some articles on it
It is your responsibility to do the search fo the information you need. Your question has been answered many times on the Forum. To be truthful experienced sellers get tired of repeating themselves every time the question comes up.
I have confidence in your ability to use the search feature.